The present invention relates to lenses having inserts defining an optical path, and more specifically to the provision of such inserts in a moulded ophthalmic lens.
Patents U.S. Pat. No. 5,886,822 and U.S. Pat. No. 6,204,974 describe systems of image combinations for eyeglasses or face masks; an image is projected towards the wearer's eye, via an optical path made in the lens; in these patents, as in the present description, the term “lens” refers to the optical system containing the inserts, which system may especially be intended to be mounted in an eyeglass frame or in a face mask. In one embodiment, this optical path is defined by inserts mounted in the thickness of the lens; the inserts proposed in those patents comprise combiners, mirrors, semi-reflective plates, polarizing beam splitter cubes, quarterwave plates, concave reflecting lenses or Mangin mirrors, diffractive lenses and holographic components. It is proposed to mount these inserts in the lens in an injection moulding, or else to machine the inserts and assemble them with the other elements of the lens. To take an example, it is proposed to form the lens from LaSFN9 having a refractive index of 1.85, or to use commercially available products having a refractive index close to that of glass (1.46). Those documents do not give more details about the way in which the inserts may be provided in the lenses.
U.S. Pat. No. 5,547,618 describes a method of moulding ophthalmic lenses; two half-moulds, made of mineral material, are provided. These half-moulds are assembled with an annular closure element. A moulding cavity is thus formed, in which a curable material is placed, for example by injecting it. The curing of the material is carried out, for example, by irradiating it with ultraviolet light. The lens formed is demoulded, after partial or complete curing.
EP-A-983 838 discloses a process for making colored contact lenses with a dazzling appearance. A pigment composition is printed to the surface of a mould. The material forming the lens is then spin-cast in the mold, before being cured. The pigment composition is dissolved wholly or in part into the material during spin-casting.
U.S. Pat. No. 33,431,327 discloses a process for making a contact lens having a metallic insert and an insert having a higher index than the material of the lens. A cutout surface is formed in a blank of material. The metallic insert or weight unit is placed therein. The higher index material is then cast in place, covering the weigh unit. The entire unit is then cured for fusing the two portions into an integral lens unit containing the weight unit. The lens is cut into this cured unit. This documents teaches against the use of adhesives, which may leach out to damage the wearer of the lens.
U.S. Pat. No. 3,967,629 discusses a method of making a contact lens blank. A circular substrate is grinded to form a curved surface. A plastic mold is formed with a surface complemental to that of the substrate and a pair of through passages. The substrate and the mold are then clamped. A curable material is poured into the passages and is cured, so as to form solid fused segments on the substrate. The plastic mold is removed and a curable material is applied to the substrate with its fused segments; the material is cured to form the blank from which the lens may be machined. The process disclosed in this document is adapted to manufacture contact lenses, by molding segments of a curable material onto a substrate.
These three documents relate to contact lenses, and not to spectacles lenses. Such contact lenses are not adapted for receiving inserts which define an optical path within the lens. The inserts referred to in these documents do not create an optical path but rather serve to weight the lens; else they are used for locally changing the refractive index of the lens—in the case of multifocal contact lenses.
EP-A-0 509 190 is directed to the manufacture of a multifocal three component glass-plastic laminated lens. The lens has a front glass layer, a back plastic layer and a segment or button embedded within the back plastic layer. An adhesive interlayer is provided between the glass layer on one hand and the back plastic layer with its embedded button on the other hand. The back plastic layer and its embedded button are formed as follows. The segment is preformed and placed in a mold. This is not the preferred technique, and there is no indication in this document of the way the segment is maintained in the mold. The monomer of the back plastic layer is injected into the mold and cured. Else, a cavity is formed with the back plastic layer; a higher index material may then be placed within the cavity and cured to form the segment.
Thus, this document does not provide any indication as to the molding of the so-called button or segment. In addition, this button or segment does not create an optical path within the lens. Rather, it locally changes the refractive index of the lens and changes the power for looking through the lens.